This invention relates to insert molding machines. Such machines make molded parts having embedded pieces, called inserts, integrally formed therein. For example, a part may have metal pieces forming electrical contacts molded within a plastic switch housing. The inserts are supported within a mold cavity on a slide prior to introduction of the molten molding material. When the part is cured the inserts, of course, are released from the slide and remain in the part.
The mold cavity is defined by the slide and two or more mold sections. At least one of the mold sections is movable between open and closed positions. One or more of the mold sections has an aperture which receives the slide. The slide is also movable between open and closed positions. In the open position the slide is retracted from the mold sections to facilitate loading of the inserts thereon. In the closed position the slide cooperates with the mold sections to define the mold cavity.
It is desirable to mechanically connect the movable mold section and slide so that only a single drive mechanism need be provided to move both parts. The mechanical connection between the movable mold section and slide causes them to open and close together. That is, opening or closing movement of a mold section simultaneously causes opening or closing movement of the slide. This has been done in the past with an angle pin entrapped in a closed slot. In effect, the angle pin and closed slot form inclined planes on the mold section and slide. Thus, vertical motion of the mold section induces horizontal motion of the slide and the two parts open and close together.
A drawback of this approach to effecting movement of the slide is that is does not permit inspection of the inserts in their final positions. Since the slide does not reach its fully closed position until the movable mold section also closes, it is not possible with conventional machines to verify that all of the inserts are properly located in the mold cavity. Sometimes slide movement will displace an insert but this cannot be seen because the mold cavity is closed when the slide finally gets to its closed position. Misplaced inserts cause defective molded parts. Hydraulically operated slides have been proposed to solve this problem but their introduction increases the complexity of the equipment and are more trouble than they are worth.